Following up discussions in thesethreads:
https://secondlifestorage.com/t-QNBBM-balancers and
https://secondlifestorage.com/t-SIMPLE-active-balancing-hardware
I've had a shot at designing an active balancer.
Please note I have not (yet) built or tested this!
Aims are:
- designed for Lithium-Ion cells, may not work on LiFePo4, my own cells are LiFePo4 ;-)
- keep it as simple as possible
- transfer energy from "full" cells only
- energy is put back into pack +ve & 0V rails
- no current flows via other cells
- select inexpensive components
- select standard resistor values
- parts used are specifically low power & low voltage
- idlecurrent should be about 1-2mA
Notes:
- it should be able to pull about 8W from the cell
- efficiency is likely >80%
- transformer design might need number of turns increasing
- it will likely have a sharp "turn-on" at the bypass voltage and may need the feedback gain tuned a bit
- it may need a small capacitor close to the pack output diode
Main partsare:
MT3608 (see eBay for modules that can be adapted)
BU7242 dual CMOS op amp
TL431A 1% regulator
Circuit diagram's here:
Discussion welcome
There's some other similar chips to the MT3608, eg PAM2421, AP1609
A mechanism to limit maximum current might be needed.
https://secondlifestorage.com/t-QNBBM-balancers and
https://secondlifestorage.com/t-SIMPLE-active-balancing-hardware
I've had a shot at designing an active balancer.
Please note I have not (yet) built or tested this!
Aims are:
- designed for Lithium-Ion cells, may not work on LiFePo4, my own cells are LiFePo4 ;-)
- keep it as simple as possible
- transfer energy from "full" cells only
- energy is put back into pack +ve & 0V rails
- no current flows via other cells
- select inexpensive components
- select standard resistor values
- parts used are specifically low power & low voltage
- idlecurrent should be about 1-2mA
Notes:
- it should be able to pull about 8W from the cell
- efficiency is likely >80%
- transformer design might need number of turns increasing
- it will likely have a sharp "turn-on" at the bypass voltage and may need the feedback gain tuned a bit
- it may need a small capacitor close to the pack output diode
Main partsare:
MT3608 (see eBay for modules that can be adapted)
BU7242 dual CMOS op amp
TL431A 1% regulator
Circuit diagram's here:
Discussion welcome
There's some other similar chips to the MT3608, eg PAM2421, AP1609
A mechanism to limit maximum current might be needed.